JPH0634590Y2 - Fuel control device for electronic fuel injection engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a fuel control device for an electronic fuel injection engine.

(Prior Art) Conventionally, as a fuel control device for an electronic fuel injection engine, an intake air flow rate detector for an engine, an intake pipe internal pressure detector and an engine speed detector as load detecting means for the engine are respectively connected to the fuel control means. However, when the intake air flow rate detector detects a predetermined intake air amount or less, the intake air flow rate sensing method (so-called, which operates the fuel injection valve based on both output signals of the intake air flow rate detector and the engine speed detector) In the intake pipe by the L-Jetronic system (hereinafter abbreviated as LJ system), which has a narrow measurement flow range but excellent measurement accuracy, and when the intake air flow rate detector detects a predetermined intake amount or more. A speed density method that operates the fuel injection valve based on both output signals of the pressure detector and the engine speed detector (so-called measurement target flow rate range is It is known that the fuel injection control is performed by a wide-range but slightly inferior measurement accuracy by a D-Jetronic system (hereinafter abbreviated as DJ system) (for example, Japanese Patent Publication No. 59-7).
(See Japanese Patent No. 017).

(Problems to be solved by the invention) However, this type of conventional fuel control device causes excessive knock and misfire due to erroneous control of fuel when the pressure detector in the intake pipe fails, which causes engine and exhaust gas purification. It could damage the catalytic converter and did not take any precautionary measures against such failures.

The present invention has been made in view of the above-mentioned problems of the related art, such as an intake pipe pressure detector for detecting an intake negative pressure downstream of a throttle valve used in a high intake flow rate region where an intake air flow rate or a load is a predetermined value or more. If the load detection means fails,
Especially, the failure of the load detecting means is caused by the LJ method and the D-method.
When the determination is made by the difference in the fuel injection amount calculated by the J method being equal to or larger than a predetermined value, the intake air flow rate supplied to the engine is forcibly limited to the predetermined value or less and the DJ area is set. It is an object of the present invention to reliably prevent the engine and the catalytic converter from being damaged due to the erroneous control of fuel in the high intake flow rate range due to the failure of the load detection means.

(Means for Solving the Problem) In order to achieve the above-mentioned object, a solution means of the present invention is an intake air flow rate detection means for detecting an intake air flow rate which is provided in an intake passage and supplied to an engine, and a throttle valve downstream. Load detection means for detecting a signal related to intake negative pressure or throttle valve opening, engine speed detection means for detecting engine speed, and fuel based on the outputs of the intake air flow rate detection means and engine speed detection means. The first fuel injection amount calculation means for determining the injection amount, the second fuel injection amount calculation means for determining the fuel injection amount based on the outputs of the load detection means and the engine speed detection means, and the intake air flow rate or load In the low intake flow rate range below the predetermined value, the second fuel injection amount calculation is performed in the high intake flow rate range above the predetermined value based on the output of the first fuel injection amount calculation means. It is premised on a fuel control device for an electronic fuel injection engine having a switching control means for operating a fuel injection valve based on the output of the means.
Then, when the difference between the fuel injection amounts calculated by the first and second fuel injection amount calculation means is equal to or greater than a predetermined value, failure determination means for determining a failure of the load detection means and intake air supplied to the engine. It is assumed to have a limiting means for limiting the flow rate to less than the predetermined value, and a limiting means driving means for receiving the output of the failure determining means and activating the limiting means at the time of determining the failure of the load detecting means.

(Operation) Accordingly, in the present invention, when the failure of the load detection means used in the high intake flow rate region is determined, the limiting means is operated to forcibly limit the intake air flow rate to less than the predetermined value. .

Embodiment An embodiment of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, the fuel injection solenoid valve 12 mounted on the intake manifold 11 that supplies intake air to the engine body 10 has a fuel pressure adjusted to a constant pressure with respect to the pressure in the intake manifold 11. Supplied and fuel control device 30
An electric current flows through the solenoid coil portion for a time controlled by, and fuel is injected from the nozzle portion. An air flow meter 13 that uses a measurement plate that rotates in response to the dynamic pressure of the intake air flow and that generates an output voltage corresponding to the rotation angle is provided in the intake pipe 15 upstream of the throttle valve 14. Mainly, it constitutes an intake air flow rate detecting means for measuring the intake air amount in medium and low load operation. On the other hand, a fuel control device is provided in the intake manifold 11 downstream of the throttle 14.
A butterfly valve 17 that constitutes intake air amount limiting means that throttles the intake air flow rate driven by a step motor 16 that is controlled by 30 to a low intake flow rate range, and boost detection as load detection means that detects intake negative pressure, that is, boost. Sensor 18 is provided. An exhaust pipe 20 includes an oxygen concentration detector 21 for detecting the air-fuel ratio and a catalytic converter 22 for purifying the exhaust gas. Further, an engine speed detector 23 as an engine speed detecting means for detecting an engine speed is provided at a distributor (not shown), and a pulse signal is generated at a crankshaft end for generating a pulse at a predetermined angular position of the crankshaft. A crank angle detector 24 as a container is provided for each.

As shown in the block diagram of FIG. 2, in the fuel control device 30 of the present embodiment, the LJ system pulse calculation circuit 31 as the first fuel injection amount calculation means has an intake air amount signal from the air flow meter 13. And an engine speed signal from the engine speed detector 23, and outputs an optimum fuel injection solenoid valve drive pulse signal in the LJ system. On the other hand, the D-J system pulse calculation circuit 32 as the second fuel injection amount calculation means receives the boost signal from the boost detection sensor 18 and the engine speed signal from the engine speed detector 23 to receive the D signal. Output a fuel injection solenoid valve drive pulse signal in the J system. Pulse difference learning circuit
33 receives the respective fuel injection solenoid valve drive pulse signals in the L-J system and the D-J system, and outputs a difference signal between the both input pulses. D- as failure judgment means
The J-system failure determination circuit 34 inputs the pulse difference signal and the boost signal and compares them with a predetermined failure determination value A obtained experimentally at each load stage, and when the pulse difference is a predetermined value A or more. The failure signal of the DJ system failure determination signals is output. In addition, the D-J method pulse correction circuit 35 is
The fuel injection solenoid valve drive pulse signal and the pulse difference signal in the DJ system are input and the solenoid valve drive pulse signal corrected corresponding to the pulse difference is output. The pulse selection circuit 36 is a normal signal of the corrected DJ fuel injection solenoid valve drive pulse signal, the LJ fuel injection solenoid valve drive pulse signal, and the DJ fault determination signal. And a boost signal are input, and the DJ type or LJ type fuel injection solenoid valve drive pulse signal corrected in accordance with the boost value is amplified by an amplifier as appropriate and the fuel injection solenoid valve 12 Output to. Also, the limiting means drive circuit
Reference numeral 37 constitutes a limiting means driving means for inputting a failure signal of the DJ system failure determination signals and outputting a driving signal to the step motor 16 so as to close the butterfly valve 17. Each of the pulse calculation circuits 31 and 32 for the L-J system and the D-J system has a read-only memory section for determining the fuel injection amount corresponding to the intake air amount or boost and the engine speed. The program is stored in advance. Further, the pulse correction circuit 35 for the DJ system is
A program for correcting the fuel injection electromagnetic valve drive pulse in the DJ system is stored in advance in accordance with the pulse difference input in each load.

The air flow meter 13 as an intake air flow rate detector is a Karman vortex flow meter that utilizes the principle that the number of Karman vortex flows increases in response to an increase in intake flow rate, or a hot wire type flow meter that measures the intake flow rate by changing the temperature resistance. It can be replaced by a meter.

Next, the operation of this embodiment will be described based on the flowchart shown in FIG. When the crank angle detector 24 or the like issues a calculation start command signal and the engine start is confirmed by the solenoid terminal voltage of the starting motor, the pulse calculation circuit 3 for the LJ system and the DJ system is used.
At 1,32, the intake air amount signal, the engine speed signal, and the boost signal are read (step P ₁ ), and the former uses the fuel injection solenoid valve drive pulse τ _L in the LJ system and the latter uses D−. The fuel injection solenoid valve drive pulse τ _D0 in the J method is calculated (steps P ₂ , P
₃ ). The drive pulses τ _L and τ _D0 for the LJ method and the DJ method are input to the pulse difference learning circuit 33, where the pulse difference Δτ _D is calculated (step P ₄ ). Then, the boost measured by the boost detecting sensor 18 is compared with a predetermined pressure B ₁ (step
P ₅ ), and if it is large, it means that the load is low, so step P ₁₁
On the other hand, when it is smaller, it is the judgment zone in the high load region, so the absolute value | Δτ _D | of the pulse difference Δτ _D is D−
In the J-system failure determination circuit 34, it is compared whether or not it is a predetermined value A or more which is experimentally determined to determine the failure (step P ₆ ). If it is the predetermined value A or more, the fail flag is set to 1 of the binary signal. Is given (step P ₇ ), and 0 is given when the value is not more than the predetermined value A (step P ₈ ). In the present embodiment, the drive pulses τ _L and τ _D0 used in the low intake flow rate region are used to improve the accuracy of failure determination. Then, it is determined whether or not the fail flag is 1 (step P ₉ ), and the fail flag is 1
When, that is, when the boost detection sensor 18 which is employed in the D-J mode has failed, the butterfly valve 17 is driven closed by limiting means driving circuit 37 (step P _10), the engine is low intake flow rate region Therefore, the fuel injection control is performed by the fuel injection solenoid valve drive pulse τ _{L according} to the LJ method (step P ₁₁ ). Further, when the fail flag is 0, that is, when the boost detection sensor 18 has not failed,
The boost measured by the detection sensor 18 is compared with a predetermined pressure B ₂ which is an experimentally determined reference value for the high flow rate region and the low flow rate region of the intake air (step P ₁₂ ), and is smaller than the predetermined pressure B ₂ In the case, that is, when the engine is operating in the medium and low load low intake flow rate region, the fuel injection control is performed by the drive pulse τ _{L according} to the LJ method (step P ₁₁ ). Further, when the boost is equal to or higher than the predetermined pressure B ₂ , that is, when the engine is operating in a high load and high intake flow rate range, DJ
By the drive pulse τ _{D obtained} by correcting the drive pulse τ _{D0 according} to the method with the pulse difference Δτ _D , efficient fuel injection control more suited to the operating state of the engine is performed (step
P ₁₃ ). Whether or not the fuel injection control is properly performed is constantly checked by the oxygen concentration detector 21 in the exhaust pipe.

In the above embodiment, the boost detection sensor is used in the DJ method, but it is also possible to calculate the load by the throttle opening detection sensor and the failure judgment of the present invention can be applied. Needless to say. A hot wire type air flow meter may be used as the LJ type air flow meter.

(Advantages of the Invention) As described above, according to the fuel control device for an electronic fuel injection engine of the present invention, the difference in the fuel injection amount calculated by the LJ method and the DJ method becomes a predetermined value or more. When the failure of the load detection means is determined by the above, it is used in the high intake flow rate range by forcibly limiting the intake air flow rate to a predetermined value or less and making it the same as the operating state in the low intake flow rate range. It is possible to reliably and effectively prevent damage to the engine and the catalytic converter due to erroneous fuel control due to a failure of the load detection means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic explanatory view of an embodiment of a fuel control device for an electronic fuel injection engine according to the present invention, FIG. 2 is a block diagram of the fuel control device of the same embodiment, and FIG. 3 is a flowchart showing a fuel injection control program in the same embodiment. 10 …… Engine body, 13 …… Air flow meter, 14 ……
Throttle valve, 17 ... Butterfly valve, 18 ... Boost detection sensor, 23 ... Engine speed detector, 30 ... Fuel control device, 31 ... LJ system pulse calculation circuit, 32 ...
D-J system pulse operation circuit, 34 ... D-J system failure determination circuit, 36 ... Pulse selection circuit, 37 ... Limiting means drive circuit.

Claims (1)

[Scope of utility model registration request] 1. An intake air flow rate detecting means for detecting an intake air flow rate which is provided in an intake passage and supplied to an engine, and a load detecting means for detecting a signal relating to an intake negative pressure or a throttle valve opening downstream of a throttle valve. An engine speed detecting means for detecting an engine speed, a first fuel injection amount calculating means for determining a fuel injection amount based on outputs of the intake air flow rate detecting means and the engine speed detecting means, and the load detecting means. And second fuel injection amount calculation means for determining the fuel injection amount based on the output of the engine speed detection means, and the first fuel injection amount calculation means in the low intake flow rate region where the intake air flow rate or load is less than a predetermined value. And a switching control means for operating the fuel injection valve based on the output of the second fuel injection amount calculation means in the high intake flow rate range above the predetermined value based on the output. In the fuel control device for the electronic fuel injection engine, the failure determination means for determining the failure of the load detection means when the difference between the fuel injection amounts calculated by the first and second fuel injection amount calculation means is a predetermined value or more. A limiting means for limiting the flow rate of intake air supplied to the engine to less than the predetermined value, and a limiting means driving means for receiving the output of the failure determining means and activating the limiting means when the failure of the load detecting means is determined. A fuel control device for an electronic fuel injection engine, comprising: